Fuse for airplane flares



y 1932- J. s. BARKER FUSE FOR AIRPLANE FLARES Filed Feb. 6. 1928 2 Sheets-Sheet l gn uexnfoz J S. arker 2 Sheets-Sheet 2 gwuz'nlioc J45. Barker J. S. BARKER FUSE FOR AIRPLANE FLARES Filed Feb 6 1928 II II Patented May 10, 1%32 2 @FFWEE JOHN S. BARKER, OF WASHINGTON, DISTRICT COLUMBIA FUSE FOR AIRPLANE FLARES Application filed February This invention relates to fuses for airplane flares and has for its object to provide a device which is simple in construction-and more eflicient in operation than those heretofore proposed.

lVith these and other objects in view the invention consists in the novel details of construction and combinations of parts which will be more fully disclosed hereinafter and particularly pointed-out in the claims.

Referring to the accompanying drawings, forming a part of this specification, in which like numerals designate like parts in all the views,

Fig. 1 is a cross-sectional view of the fuse taken on its longitudinal axis with the parts in safe or inoperative position;

Fig. 2 is a cross section taken as on the line 22 of Fig. 1 and looking in the direction of the arrows; and

Fig. 3 is a crosssection taken as on the line 33 of Fig. 1 and looking in the direction of the arrows; and

Fig. 4 is a view similar to Fig. 1 but illustrating the parts in operative or firing posltion.

' The airplane flare is believed well known, but may be briefly described as a pyrotechnic device giving illumination of such intensity that a large area is lighted sufiiciently to permit of photographing, reconnoitering, bombing, night landings, etc. More specifically, and in its preferred form, it consists of a metal tube containing a candle attached to a folded parachute. The candle is usually made of finely divided magnesium with the addition of other substances, serving as a binder, pressed into a solid mass inside of a tube of cardboard or other material that will burn away as the magnesium is consumed. One end of the candle isopen and usually faced with a starting mixture of pyrotechnic powder more readily ignited than the pressed magnesium. The opposite end of 6, 1928. Serial No. 252,396.

the candle, to Which the parachute is attached, is closed.

The metal tube is provided with a threaded opening in its nose end for insertion ofthe fuse, the opposite end being closed by a readily yieldable cover so that the candle and parachute can be easily expelled. .Vanes are attached exteriorly of the metal tube or case at the ejection end so that in fallingaway from the airplane the flare will be caused to assume a course parallel toits own axis with the fuse end forward. After ejection the candle, suspended by the parachute, provides an illumination of about 500,000 candlepower which will last without diminishing for about seven minutes. a p The fuse, forming the subject matter of this invention, is a mechanismby which the candle is ignited and both the candle and parachute expelled from the metal case after the flare has fallen a certain distance from the airplane. 'It consists essentially of acylindrical barrel 1 provided exteriorly with threads 2 by means of which it is fastened to the flare case, an extending flange 3 serv- 7 ing as a stop to correctly position the fuse. 4 is a shaft having secured rigidly to one end thereof, as by a rivet 5, a-propeller 6 which may be conveniently formed from a single sheet of metal. Any means for preventing an undesired rotation of said shaft may be employed, Fig. 2 illustrating a simple means wherein the shaft is flattened as at 7 on opposite sides in a portion of its length outside the barrel 1, said flattened portions adapted to be engaged by a fork carried by the airplane, whereby rotation of the propeller shaft is prevented until after the flare has been released. a

The propeller shaft is in threaded engagement with the barrel 1 and adapted to be forced within said barrel through the instrumentality of the propeller 6, the blades of which are rotated by the action of the air through which the flare is falling after its release from the airplane. The end of the shaft 4 opposite the propeller is axially bored to slidingly receive a firing pin 8 having a tubular body portion into which extends a compression spring 9 located in the bored shaft 4:. The portion of the propeller shaft surrounding the firing pin is adapted toslidingly engage the bore 10 of the central portion of the fuse barrel and is provided with a transverse bore for containing two steel balls 11 which are of such diameter as will permit them to be located on opposite sides of the pointed end of the firing pin 8 and to hold the same in inoperative position against the compression of the spring 9. That is to say, the bevelled shoulder formed between the tubular body portion and the pointed end of the firing pin will rest on the balls 11 when said pin is in inoperative position because each ball has a diameter greater than the thickness of the wall of the propeller shaft in which it is located, and there fore each ball will extend into the bore provided for the firing pin.

The barrel 1 at the end opposite the propeller is provided with an axial bore 12 of a diameter greater than the central bore 10, and the outer extremity of the former is 7 threaded to receive a metallic housing 13 containing a fulminate cap or primer 14, a

charge of powder compressed into a solid [cake 15, and a'small charge of loose powder 16, the powder being retained in said housing by an inner disc 17 of waterproofed paper or cloth and an outer disc: 18 of metal having a central hole. Both discs are suitably retained in position as by crimping over the end of the ejection charge housing 13 as clearly shown. The diameter of the bore 12 is such that when the transverse bore of the propeller shaft 4 has reached the same, the balls 11' will be radially moved'outof the way of the firing pin by the bevelled or taper surface thereof, whereupon said pin is projected by the force of the spring'9 against the 'fulminate cap 14 to explode the same, the spark therefrom igniting the loose powder 16 which in turn will ignite the compressed'powder 15. a

The operation of this device should be clear from the foregoing, but may be stated as follows. When the flare is placed in the dropping gear of an airplane some member of the dropping gear engages either the propeller or the propellerv shaft of the fuse to prevent rotation of the same while the flare is attached to the airplane. After the flare is fastened in the dropping gearand the propeller holding member is in place, thecotter pin 20 is withdrawn from the propeller shaft so that after release from the airplane, the

propeller shaft will be free to rotatingly advance into the barrel 1 of the fuse.

As the fiare'falls from the 'airplane'it will on the outer surface thereof at the ejection end, with the fuse disposed at'the lowermost portion of the flare, and in its continued fall the propeller blades 6 will be rotated by the rush of air therethrough. This causes the propeller shaft to rotate and advance on its threads into the fuse barrel from the position shown in Fig. 1 to the position shown in Fig.

4: in which latter position the fuse is operative. balls 11 reach the shoulder between the two bores 10 and 12 of the barrel 1, the threads of the propeller shaft become disengaged with those of the barrel 1, and the said shaft may continue on its travel inwardly of said barrel due to the air pressure on the blades of In other words, as the center of the.

the propeller. When the balls reach and pass a said shoulder, the action of the spring 9 causes the bevelled shoulder of the firing pin 8 to force the balls radially through the transversebore of the shaft 4:, and out of the way to permit said firing pin under pressure'to strike the primer.

On being so struck, the primer is ignited and sends a flash of flame into the ejection charge which in turn explodes, igniting the candle of the flare and ejecting both the candle and parachute from the flare case. The major portionof the ejection-charge 15 is compressed into a solid cake to reduce the violence of the explosion. The distance from the airplane at which this fuse will; function depends on the size and numberof blades" in the propeller 6 and on the number of turns required by the propeller shaft to reach the firing position, :and therefore it is obvious that fuses may be readily: des1'gned,;by changes of dimensions, to function fit any desired distance from the airplane.

Former fuses for flares have provided no.

plosive elements are absolutely sealed againstmoisture. g

. This is of vital importance .especiallyin connection with flares carried. by seaplanes which are attached below the wing 'and"usu-; ally drenched with water as the plane takes off.

V 7 From the foregoing it willthus'be seen that by this invention there is provided an Iimproved fuse for airplane flares of. the screw '5 propeller .type employing propulsive meansfor igniting the charge.

pulsive means will be seen-toincludethe fir? Further/the "pro- 10.; means for striking a percussion primer but I ing pin 8 controlled by the pressure of the spring 9 and telescopically associated with the shaft 4, as well as the balls 11 which coact with an inclined shoulder of the firing pin to retain said pin in inoperative position while the end of the shaft in which are located the balls is in sliding engagement with the smaller bore 10 of the barrel 1. When the shaft 4 has advanced into the barrel under pressure of the air on the screw blades 6 a predetermined distance then the balls 11 will be moved radially by the said inclined shoulder of the firing pin under action of the spring 9, said balls occupying space outside of the end of the shaft 4 within the other bore 12 of said barrel. At this time the spring 9 is strong enough to propel the firing pin into ignition and contact with the percussion cap 1%. Further it will be seen that the release of the firing pin is caused at a predetermined position of the screw or shaft 4 or in other words, the propulsive means is released by the screw when the same has advanced into the barrel a certain distance, the balls 11 serving as a latching means to hold the firing pin under pressure in inoperative position until the predetermined position of said screw is reached.

It is obvious that those skilled in the art may vary the details of construction as well as arrangements of parts without departing from the spirit of the invention, and it is therefore not desired to be limited to the foregoing except as may be required by the claims.

What is claimed is 2- 1. In a fuse for airplane flares the combination of a barrel provided with two coaxial bores of different diameters; a shaft in threaded engagement with said barrel and provided with a cylindrical end portion slidingly coacting with the smaller barrel bore, the wall of said end portion having a passage therethrough; a ball in said passage; means for rotating said shaft to advance the same into said barrel; an explosive mixture carried by said barrel having associated therewith a percussion cap; and propulsive means for igniting said mixture, said means including a firing-pin held in inoperative position by said ball when said end portion is within the smaller barrel bore but released to strike said percussion cap when said end portion enters the larger barrel bore by transverse movement of said ball in said passa e.

g In a fuse for airplane flares the combination of a barrel provided with two coaxial bores of different diameters; a shaft in threaded engagement with said barrel and provided with a cylindrical end portion slidingly coacting with the smaller barrel bore, the wall of said end portion having a passage therethrough; a ball of a diameter greater than the thickness of said wall in said passage; means for rotating said shaft to advance the same into said barrel; an explosive mixture carried by said barrel; and propulsive means for igniting said mixture, said means including a spring actuated firingpin held in inoperative position by an inclined shoulder on said pin contacting with said ball when said end portion is Within the smaller barrel bore but released to strike said percussion cap when said end portion enters the larger barrel bore by transverse movement of said ball in said passage caused by said shoulder.

In testimony whereof I affix my signature.

JOHN S. BARKER. 

